Electrochemical reforming of CH4−CO2 mixed gas using porous Gd-doped ceria electrolyte with Cu electrode

This paper reports on the composition and flow rate of outlet gas and current density during the reforming of CH4 with CO2 using three different electrochemical cells: cell A, with Ni−GDC (Gd-doped ceria: Ce0.8Gd0.2O1.9) cathode/porous GDC electrolyte/Cu−GDC anode, cell B, with Cu−GDC cathode/ porous GDC electrolyte/Cu−GDC anode and cell C, with Ru−GDC cathode/ porous GDC electrolyte/ Cu−GDC anode. In the cathode, CO2 reacts with supplied electrons to form CO fuel and O2− ions (CO2+2e−→CO+O2−). Too low affinity of Cu cathode to CO2 in cell B reduced the reactivity of the CO2 with electrons. The CO fuel, O2− ions and CH4 gas were transported to the anode through the porous GDC mixed conductor of O2− ions and electrons. In the anode, CH4 reacts with O2− ions to produce CO and H2 fuels (CH4+O2−→2 H2+CO+2e−). The reforming efficiency at 700−800 °C was lowest in cell B and highest in cell A. The Cu anode in cells A and C worked well to oxidize CH4 with O2− ions (2Cu+O2−→Cu2O+2e−, Cu2O+CH4→2Cu+CO+2H2). However, a blockage of the outlet gas occurred in all the cells at 700−800 °C. The gas flow is inhibited due to a reduction in pore size in the cermet cathode, as well as sintering and grain growth of Cu metal in the anode during the reforming.